Electrical discharge device



Aug. 25, 1953 A WQQD ELECTRICAL DISCHARGE DEVICE 2 Sheets-Sheet 3;

Filed April 22, 1950 FiG.5.

INVENTOR. RUS A W ATTORNEY Aug. 25, 1953 R. A. WCDOD 2,650,323

ELECTRICAL DISCHARGE DEVICE Filed April 22, 1950 2 Sheets-Sheet 2 FIG.4.

IN V EN TOR.

A T RNEY Patented Aug. 25, 1953 ELECTRICAL DISCHARGE DEVICE Russell A.Wood, South Milwaukee, Wis., assignor to McGraw Electric Company,Milwaukee, Wis., a corporation of Delaware Application April 22, 1950,Serial No. 157,542

8 Claims.

This invention relates to electrical discharge devices and moreparticularly to lightnin arresters of the expulsion type for use onelectric power distribution systems.

The present invention is incorporated in a housing structuresubstantially identical to that shown in Pat. No. 2,429,533, granted toHerman O. Stoelting, on October 21, 1947, and assigned to the assigneeof the present invention.

As was pointed out in the above patent, there are two factors affectingthe bore diameter of the arc extinguishing expulsion tube. One of thesefactors, namely surge capacity, requires a chamber structure that willwithstand any pressure enerated by heavy surges. It is apparent thathigh surge capacity may be achieved by providing a tube with a chamberhaving a large bore or by a structure that is internally strong orreinforced in some manner. The other factor affecting bore is, namely,the ability to extinguish low current arcs, which require a smaller boreor a more confined space. Low current arcs ordinarily do not producesumcient gas from an enlarged bore surface to disperse the ions orconductive arc gases and prevent the re-establishment of the arc.

It is therefore an object of the present invention to provide anexpulsion type lightning arrester with a reinforced arcing chamber thatis of arc-extinguishing material, said chamber containingarc-extinguishing materials within, arranged in such manner as toprovide a multiplicity of passages between arcing electrodes in order toreconcile the opposing factors of lateral pressure caused by heavysurges, While at the same time providing relatively confined passagesfor low current arcs.

A further object of the invention is to provide an expulsion lightningarrester with a plurality of lateral passages within the arc-expulsionchamber, the passages being relatively free to expand and contract inorder that pressure exerted by an initial surge will act to restrictfollow current from traveling between arcing electrodes through eitherthe gas filled passage or remaining passages which have been tightlyconfined because of said pressure.

In the drawings:

Fig. l is a longitudinal view, partially in section, of the expulsiontype arrester depicting the preferred embodiment of the presentinvention;

Fig. 2 is a cross-sectional View taken at 2-2 of Fig. 1 illustrating theuse of stacked sheets of arc-extinguishing material cut to substantiallyfill the bore diameters of the arcing chamber of the lightning arrester.

Fig. 3 is a cross-sectional view of a modification of the preferredembodiment taken on a plane substantially the same as that of Fig. 2,which modification illustrates a spirally wound sheet ofarc-extinguishing material wound around a small rod of the same materialextending the full length of the arcing chamber.

Fig. 4 is a longitudinal view, partially in section, of a lightningarrester illustrating another modification of the present invention.

Fig. 5 is a cross-sectional view taken on 55 of Fig. 4.

Fig. 6 is a top plan view of the lower electrode vent plug, whichprovides a means for retaining the arc-extinguishing material whilepermitting gas to escape.

The embodiments of the arrester disclosed in Figs. 1 and 4 aresubstantially identical as pertains to the arrester housing andspark-gap arrangement, the novelty of the present invention lying in theconstruction of the arc-extinguishing expulsion chamber. Therefore, likeparts in both embodiments will be designated by the same referencecharacters.

The housing portion l is preferably of porcelain, and is provided with achamber 2 which is nearly coextensive with the housing. At the upper endof the housing there is provided an aperture 3 which accommodates a studl. This stud is electrically connected to a washer 5 which makes contactwith an elongated electrode member 6 that is clamped to the lower end ofa petticoat insulator I. The insulator is anchored to the upper end ofthe stud 4 which is firmly imbedded therein.

A line terminal 8 is fastened to the upper extremity of the insulator I,and is adapted to engage a conductor wire connecting with the power linethat is to be protected. An electrode member 9 is secured to the upperend of the insulator 1 making electrical contact with the terminalmember 8 which also serves to hold this electrode member in position. Anopen sparkgap E0 is formed by the spacing of the free ends of bothelectrode members 5 and 9. Though an open spark-gap arrangement as shownis preferable, it is also feasible and may be equally expeditious toprovide an internal spark-gap arrangement (not shown). The spark-gap isnot part of the present invention, but is necessary for isolating thenovel expulsion tube from the line terminal 8, thereby preventingleakage currents from flowing to ground through the expulsion tube andassociated parts.

A gasket II is provided as a clamping cushion between the insulator land the housing member i, to prevent chipping of the porcelain when theparts are drawn together. This gasket is also provided as amoisture-proof seal.

Within the chamber 2, the lower end of the stud 4 is threaded to engagewith a threaded opening in the metal arcing electrode plug I2. Thiselectrode plug I2 is threaded externally to engage with thecomplementary internally threaded end of a tubular retainer member I3 ofinsulating material, preferably of horn fiber. The tubular retainermember It is reinforced by a metal sleeve I i surrounding that member,with its upper extremity at a plane approximately level with the lowerextremity of the electrode plug I2. The lower portion of the electrodeplug I2 has an electrode portion I211 which accommodates a fiber washerl5 having an external diameter substantially identical to that of theelectrode plug E2.

The lower end of the retainer member I3 is externally threaded to engagea flanged fitting I8, which serves concurrently as a closure for thechamber 2, a support for the novel arc-extinguishing materialhereinafter described, and as a lower terminal member to which theground wire (not shown) is connected. A gasket I1 is provided betweenthe porcelain housing I and the fitting It to act as a cushion topreventbreakage or chipping of the porcelain.

The lower end of the sleeve I l rests on the bearing surface of thefitting I6, and extends to a plane substantially coinciding with theplane of the lower surface of the electrode plug I2. This metal sleeveI4 also acts to reduce the impulse sparkover of the arrester. It isapparent that the external fiashover-voltage of the expulsion tube mustbe higher than the internal flashover-voltage. If this were not so, anylightning or line surges would take the easier external path rather thanthrough the effective extinguishing media positioned internally withinthe retainer member 13. Thus, the sleeve length is restricted to end asclose as possible to the plane of the lower edge of the plug I2, butstill positioned so that the nearest edge lilof this plug is at adistance from the upper extremity of the sleeve I9 so that it will keepthe external fiashover-voltage at a. higher value than the internalfiashovervoltage. The fiber washer I5 is used to prevent the are frominitiating along the inner wall of the retainer member I3, and it may bevaried in dimensions, both in thickness, length and diameter, to providethe proper dielectric-stress distances between the edge I8 of electrodeplug I2 and upper extremity IQ of sleeve IQ for retaining desiredfiashover-voltage values. The fiber tubular retainer member I3 isextended above the electrode plug I2 to provide a chamber 20. Thischamber 20 is provided as a means of increasing the flashover distancebetween the various upper electrode parts and the sleeve I l. Thus, theflashover value between the sleeve l4 and the upper electrode I2 may bekept at a higher value than the internal spark-over value between thearcing electrode plug I2 and electrode arcing vent plug 23 by varyingthe length of the chamber 20 to correspond to the desired internalspark-over value- Thus, the arc may be confined to the arcing areas inthe arc-extinguishing media, or medium, where it may be properlyextinguished.

The metallic fitting I8 is provided with a discharge port H forreleasing gases to the atmosphere. The fitting is also provided with ameans for connecting the arrester with ground. This is shown in Figs. 1and 4 as a solderless connector in the form of a bolt 22 engaging with acomplementary threaded opening in the fitting I6. The fitting also seatsan electrode arcing vent plug 23, as shown in Fig. 6, and is inelectrical contact with it. The. plug 23 is provided with a plurality ofdischarge openings 2% and a fiber washer 25. The remaining surface area26 of the plug and the washer surface serve to support the novelarcextinguishing media as hereinafter described. The fiber washer 25acts to seat the electrode plug 23 within the bore of the retainermember I3, and also to minimize arcing at the outer diameter of theplug, thereby causing the arc to follow the most desirable path throughthe center portion where the arc may be properly extinguished.

Referring particularly to Figs. 1 and 2, this invention contemplates theuse of a novel arcextinguishing media comprising a series of thinadjacent strips of horn fiber 36. These fiber strips are preferably inthe form of strips or the same length, but of varying widths, arrangedto provide a plurality of wall surfaces defining the arc passages SI andsubstantially filling the internal diameter of the retainer member I3 asdisclosed by Fig. 2. The lengthwise extremities of the fiber sectionsextend laterally to a plane level with each of the opposed internal fiatsurfaces of the electrode plugs I2 and 23 as shown in Fig. 1. The arcingdistance between the electrode plugs I2 and 23, and consequently thelength and width of the fiber strips 30, may vary according topredetermined conditions established for proper protection of associatedequipment. It is to be noted that passages 3| between the adjacent fiberstrips 30 are spaced to permit a part of the section to respond flexiblyto any pressures exerted within any space or spaces. It will be apparentfrom the drawings, especially Figs. 1 and 2 that the passages 3| areprovided by light surface contact between the wall members or strips 30.In addition, it is an inherent characteristic of unpolished horn fiberto have a surface with a multiplicity of high spots. The light surfacecontact between adjacent fiber wall members offers excellent high-spotcontact between wall members, which, in turn, provides the idealpass-age for supporting spark-over between electrode plugs !2 and 23.

The arrester operates as follows: When a surge occurs on the power lineand is of high enough potential it will simultaneously sparkover theexternal gap ill and the internal expulsion gap between the arcingelectrode plug I2 and the electrode vent plug 23 which is electricallyconnected with ground,

Under certain conditions the surge may initiate the flow of power followcurrent, and it is necessary to extinguish this power follow current arcin order that the arrester may return to its original operatingcondition. To accomplish this, this invention contemplates the use of anovel media contained within the retainer member I3 and extendinglaterally between the electrode plugs I 2 and 23.

The are is initiated between any two arcing passages 3I between thefiber strips 363. The spark-over from electrode plug I2 to electrodeplug 23 due to rapid rise in voltage tends to be the lowest for tWoclosely packed sections of fiber. This insures initiation of the arcsomewhere within the area bounded by the retainer member I3 which areais further confined to the center of the arcing chamber by the washersI5 and 25.

Horn fiber strips 30 are employed, because when subjected to an arc theywill emit gas or vapor which is well-known for its arc-extinguishingproperties. The arrangement of the arc-extinguishing media effectivelyprovides gas or vapor which evolves very rapidly and in a volumeadequate to deionize the arc path or, at least, to so disperse the ionsor break up the continuity or density of ionization that the arc will beextinguished at first current zero and will not restrike.

The power current, which is normally 60-cycle current, produces an arethat tends to follow the path taken by the abnormal surge voltage thatsparked over the arrester, and will tend to be confined to one of thepassages 3| between the fiber strips 30 where it will be limited,cooled, and rapidly extinguished at first current zero.

It was found that erosion of the fiber media tends to be uniform. Sincegases formed are confined, they will move the fiber strips 30 apartforcing adjacent sections to become very tightly confined. When apassage 3| between two of the strips 39 is enlarged due to erosion it isthe tendency of subsequent surge to initiate between two other tightsections of fiber because sparkover is always lower between two closelypacked sections and consequently the erosion is spread uniformly amongthe sections. The arcs created by both abnormal voltage surges andfollow current are extinguished, cooled and expelled in the arcingpassages 3| and the gas and vapor is vented through openings 24 of thearcing electrode plug 23 to the discharge port 2 of fitting l5 where itis expelled to the exterior. The current flows freely to ground throughthe ground Wire (not shown) connected to connector 22.

Figs. 3, 4, and 5 illustrate effective modifications of the novelarc-extinguishing media. Obviously, as emphasized in the description ofthe strip-like arc-extinguishing material shown in Figs. 1 and 2, thewall surfaces of the modifications hereinafter described are in lightsurface contact with each other. This light contact between theunpolished fiber surfaces offers an excellent passage for initiatingspark-over. Fig. 3 shows a sheet of horn fiber material 40 rolled aroundthe full length of a round fiber rod 42, extending between the upperelectrode plug l2 and the lower electrode plug 23 of Fig. 1. Each of thewinding turns of the spiral forms a flexible wall surface, two adjacentturns of fiber providing an infinite number of arcing passages 4|between electrode plugs I2 and 23. It is again to be noted that thefiber is rolled loosely enough to permit flexible response to expandinggases formed within arcing passages 4|. The action of this modificationis substantially identical to that of the fiber strips 30 of Figs. 1 and2, the surge and follow current passing in the arcing passages 4|provided by adjacent windings of fiber material 40 from the electrodeplug |2 to the electrode plug 23.

Figs. 4 and 5 illustrate a further modification of the novel arcingmedia. Here, the surge spark-over initiates in either one of thecircular passages 45, 46, 41, or 48 as defined by tubular wall membersof horn fiber 49, 59, 5| or the fiber rod 52 contained within theretainer member l3. The arc-extinguishing wall members 49, 50, and 5|are in the form of telescoped concentric tubes extending between theelectrode plugs 12 and 23. The concentric tube sections are, again, not

tightly confined in order to permit movement about the center rod 52.The electrode plugs I2 and 23 are countersunk slightly at the center ofeach of the opposing surfaces to provide supports 53 and 54 at theextremities of the rod 52. It is apparent that though three telescopedtubular wall members 49, 50, and 5| are shown, a greater or lessernumber of concentric tubes may be used with effective results.

The gases or vapor formed in the arc initiating passage forces thetelescoped tubes to move into eccentric relation thus forming a crescentshaped passage which starts from a narrowly confined area to arelatively distended area diametrically opposed to the other, Thus, itsoperation will be substantially identical to that of the preferredembodiment shown in Figs. 1 and 2.

It will be apparent that an expulsion-type lightning arrester isprovided that has a high surge capacity and will operate to effectivelydischarge abnormal surge currents and extinguish subsequent followcurrents associated therein and will adequately protect transformers andassociated equipment.

I claim:

1. In a discharge device for electric lines an insulating tube closed atone end and open at the other, said tube defining an arcing chamberhaving a plurality of adjacent wall members laterally relative to eachother, substantially the entire wall surfaces of adjacent members beingnormally in light surface contact with each other defining a pluralityof laterally adjacent sparkover passages and having the capacity to emiteffective quantities of arc-extinguishing gases when subjected to hightemperatures, said wall members each characterized by a thin dimensionnormal to said wall surfaces of said members thereby to permit flexingof the wall laterally of the passage to form an arcing passage inresponse to pressure exerted by said gases, and an electrode member ateach extremity of said wall members, one of said electrode membersexposed to said chamber at the closed end, the other of said electrodemembers being disposed at the open end of said chamber and vented todischarge gases generated within said passages.

2. in a discharge device for electric lines an insulating tube closed atone end and open at the other, said tube defining an arcing chamberhaving in effect a plurality of layer upon layer of adjacent wallsections laterally relative to each other, substantially the entire wallsurfaces of adjacent sections being normally in light surface contactwith each other defining a plurality of laterally adjacent spark-overpassages and having the capacity to emit eifective quantities ofarc-extinguishing gases when subjected to high temperatures, said wallsections each characterized by a thin dimension normal to said wallsurfaces of said sections thereby to permit a degree of flexibleresponse to gas pressures created within said spark-over passages toform an arcing passage, and an electrode member at each extremity ofsaid wall sections, one of said electrode members exposed to saidchamber at the closed end and the other of said electrode members beingdisposed at the open end of said chamber and vented to discharge gasesgenerated within said passages.

3. In a discharge device for electric lines an insulating tube closed atone end and open at the other. said tube defining an arcing chamber, twoelectrode members, one of said electrode members exposed to the chamberat the closed end and the other electrode member being disposed at theopen end of said chamber and vented to discharge gases generated withinsaid arcing chamber, said arcing chamber having a plurality ofstrip-like members defining a plurality of laterally adjacent spark-overpassages extending between said electrode members and composed of amaterial capable of emitting effective quantities of arc-extinguishinggases when subjected to high temperatures, adjacent strip-like membersnormally in light surface contact with each other throughoutsubstantially their entire surface areas and arranged to substantiallyfill the internal bore of said arcing chamber, said strip-like memberscharacterized by a thin dimension normal to said spark-over passagesdefined by said strip-like members thereby to permit flexing of the walllaterally of the passage to form an arcing passage in response topressure exerted by said gases.

In a discharge device for electric lines an insulating tube closed atone end and open at the other, said tube defining an arcing chamber, twoelectrode members, one of said electrode members exposed to the chamberat the closed end the other electrode member being disposed at the openend of said chamber and vented to discharge gases generated within saidarcing chamber, said arcing chamber having a plurality of substantiallyconcentric layer upon layer of adjacent wall portions, the Wall surfacesof adjacent layers being normally in light surface contact with eachother throughout substantially their entire surface areas defining aplurality of laterally adjacent spark-over passages .and having thecapacity to emit effective quantities of arc-extinguishing gases whensubjected to high temperatures, said wall portions each characterized bya thin dimension normal to said wall surfaces thereby to permit flexingof the wall laterally of the passage to form an arcing passage inresponse to pressure exerted by said gases.

5. In a discharge device for electric lines an insulating tube closed atone end and open at the other, said tube defining an arcing chamber, twoelectrode members, one of said electrode members exposed to the chamberat the closed end and the other electrode member being disposed at theopen end of said chamber and vented to discharge gases generated withinsaid arcing chamber, said arcing chamber having contained therein asheet embodying an arc-extinguishing material wound spirally relative toa radial plane substantially filling the internal bore of said chamber,the surfaces of adjacent convolutions of saidsheet normally in lightsurface contact one with another throughout substantially the entiresurface area and defining a plurality of laterally adjacent spark-overpassages, said sheet characterized by a thin dimension normal to saidsurfaces thereby to permit flexing of the sheet laterally of the passageto form an arcing passage in response to pressure exerted by said gases.

6. In an excess voltage discharge device com prising a housing andisolating gap electrodes carried thereby, the combination with aninsulating tube in said housing of arcing electrode members adjacenteach end of said tube, an arc-extinguishing medium within said tube,said medium comprising a plurality of adjacent wall members laterallyrelative to each other and extending between said arcing electrodemembers, the wall surfaces of said members normally in light surfacecontact with each other throughout substantially their entire surfaceareas defining a plurality of laterally adjacent spark-over passages,said wall members characterized by thin dimension normal to said wallsurfaces of said members thereby to permit flexing of the wall laterallyof the passage to form an arcing passage in response to pressure exertedby said gases.

7. In a discharge device for electric lines comprising a housing andisolating gap electrodes carried thereby, the combination of aninsulating tube contained within said housing, said insulating tubedefining an arcing chamber closed at one end and open at the other, twoelectrode members, one of said electrode members exposed to the chamberat the closed end and the other electrode member disposed at the openend and vented to discharge gases generated within said arcing chamber,said arcing chamber having a plurality of strip-like members defining aplurality of laterally adjacent spark-over passages extending betweensaid electrode members and composed of a material capable of emittingeffective quantities of arc-extinguishing gases when subjected to hightemperature, adjacent strip-like members normally in light surfacecontact With each other throughout substantially their entire surfaceareas and arranged to substantially fill the internal bore of saidarcing chamber, said strip-like members characterized by thin dimensionnormal to the spark-over passages defined by said strip-like membersthereby to permit a degree of flexible response to gas pressure to forman arcing passage.

8. An excess voltage discharge device comprising a housing, an insulatormember secured to one end of said housing, said insulator mem berprovided with elongated electrode members at each end thereof, saidelongated electrode members adapted to provide an isolating gap, saidhousing including an insulating tubular retainer member, said retainermember containing an arcing chamber closed at one end and open at theother, spaced electrodes at either end of said arcing chamber, one ofsaid electrodes electrically connected in series with said isolating gapand exposed to the arcing chamber at the closed end, and the otherelectrode positioned at the open end and vented to discharge gasesgenerated Within said arcing chamber, said arcing chamber containing anarc-extinguishing medium having in effect a plurality of layer uponlayer of adjacent wall sections laterally relative to each other, thewall surfaces of said sections normally in light surface contactthroughout substantially the entire surface area and defining aplurality of laterally adjacent spark-over passages and having thecapacity of emitting effective quantities of arc-extinguishing gaseswhen subjected to high temperatures, said wall sections characterized bya thin dimension normal to said wall surfaces of said sections therebypermitting a degree of flexible response to gas pressures created withinsaid spark-over passages to form an arcing passage.

RUSSELL A. 'W'OOD.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,923,748 Roman Aug. 22, 1933 2,050,397 Torok Aug, 11, 19362,338,479 Ackermann Jan. 4, 1944 2,391,758 Wade et al. Dec. 25, 19452,429,533 Stoelting Oct, 21, 1947

